Cystic fibrosis (CF) is the most common lethal genetic disease of Caucasian children. The basic defect is not known nor is there an assay for the CF genotype suitable for genetic counseling. Various factors have been reported in CF patient material which may be markers for the disease. We have isolated a ciliostatic fraction (CDF) from CF saliva which inhibits mammalian debranching enzyme. Our laboratory and others have reported altered enzyme activities and metabolite levels in CF patient materials. We suggest that some of these altered activities may be due to the effect of the CF factor(s) on enzyme action or enzyme secretion. The goal of the proposed research is to determine if the salivary CDF is the basis for any of the reported alterations in CF enzyme activities. Fractions corresponding to the CDF activity in CF saliva will be isolated from CF homozygote (CF), CF heterozygote (H) and normal (N) saliva samples. These fractions will be tested to determine if they affect erythrocyte membrane ATPase, arginine esterase, glutathione reductase, diamine oxidase, and other enzymes whose activity is reported to be altered in CF. The proposed experiments should define the role of the salivary CDF in the pathogenesis of CF, and may explain the basis for some of the altered enzyme activities. The CDF fractions from CF, H, and N saliva will also be tested on enzymes which, like debranching enzyme, are particularly sensitive to inhibition. The effect of CDF on these enzymes and those tested due to alteration in CF will be compared to determine the enzyme most suitable for assay of CDF concentrations directly in patient materials. A quantitative assay for CDF based on its effect on this enzyme will be developed. This assay will be used to measure the CDF concentration in CF, H, and N saliva, to determine if CDF levels can be used as the basis for genetic counseling.